IMPERFECTIONS IN METALS
DOE-HDBK-1017/1-93
Structure of Metals
The important information in this chapter is summarized below.
Microscopic Imperfections
Point imperfections are in the size range of individual atoms.
Line (dislocation) imperfections are generally many atoms in length. Line
imperfections can be of the edge type, screw type, or mixed type, depending on
lattice distortion. Line imperfections cannot end inside a crystal; they must end
at crystal edge or other dislocation, or close back on themselves.
Interfacial imperfections are larger than line imperfections and occur over a two
dimensional area.
Interfacial imperfections exist at free surfaces, domain
boundaries, grain boundaries, or interphase boundaries.
Slip occurs when a crystal is subjected to stress and the dislocations march
through the crystal until they reach the edge or are arrested by another
dislocation.
Macroscopic Defects
Bulk defects are three dimensional defects.
Foreign particles included in the prime material (inclusions) are most
common bulk defect
Gas pockets
Shrinking cavities
Welding or joining defects
MS-01
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